10. Patek Philippe reference 1591

Price tag: $2,263,964

Yes, indeed. This normal-looking watch was sold at an auction for well over $2 million. It immediately became the most expensive stainless-steel watch ever sold. If you ever inherit a Patek Philippe in stainless steel, then you'd better take care of it. Patek Philippe watches in steel are more rare than their siblings in gold and therefore fetch incredibly high prices at auctions.